Monday, May 01, 2006

Hawker-Siddeley Harrier

The Hawker-Siddeley Harrier and the AV-8A are the first generation of the Harrier series, a revolutionary close-support and reconnaissance fighter aircraft with unique V/STOL capabilities. The family is part of a large family of experimental versions and service aircraft, including the much modernized Harrier II.The Harrier family was started with the Hawker P.1127. Design began in 1957 by Sir Sidney Camm, Ralph Hooper of Hawker Aviation and Stanley Hooker of the Bristol Engine Company. Rather than using rotors or a direct jet thrust the P.1127 had an innovative vectored thrust turbofan engine and the first vertical take-off was on October 21, 1960. Six prototypes were built in total, one of which was lost at an air display.An order for 60 aircraft was received from the RAF in 1966, and the first pre-production Harriers were flying by mid-1967.The Harrier GR Mk.1 was the first production model taken from the Kestrel, it first flew on December 28, 1967, and entered service with the RAF on April 1, 1969. The ski-jump technique for STOL use by Harriers launched from Royal Navy aircraft carriers was tested at the Royal Navy's airfield at Yeovilton, Somerset. Their flight decks were designed with an upward curve to the bow following the successful conclusion of those tests. The air combat technique of vectoring in forward flight, or viffing, was evolved in the Harrier to outmaneuver a hostile aircraft or other inbound weapon. The Harrier GR.3 featured improved sensors, countermeasures and a further uprated Pegasus Mk 103 and was to be the ultimate development of the 1st generation Harrier. This model saw extended service in the Falklands War.The Harrier has two control elements that a fixed wing aircraft does not normally have. These are the thrust vector and reaction control. The thrust vector is the angle of the four engine nozzles and can be set between zero degrees (horizontal, pointing straight back) and 98 degrees (pointing slightly forwards). The 90 degree position is generally used for VTOL manouvring. Thrust vector is adjusted by a control similar to and beside the thrust lever. The reaction control is achieved by manipulating the control stick and is similar in action to the cyclic control of a helicopter. While irrelevant during forward flight mode, these controls are critical during VTOL and STOL, and are used together during these manouvres. Wind direction and the orientation of the aircraft to this is also critically-important during VTOL manouvres (in this sense operation is limited compared with a helicopter, which can take off and land in side winds). The Harrier's landing gear configuration also complicates normal landing; it is necessary to ensure that the wing-mounted stabiliser struts contact the runway simultaneously; bounce or skew to one side can result if this is not achieved. The Sea Harrier, which is based on the GR3, was important in the British victory in the Falklands War. Twenty Sea Harriers were operated from the carriers HMS Hermes and Invincible mainly for fleet air defence. Although they destroyed 23 Argentine aircraft in air combat (in part due to using the American-supplied latest variant of the Sidewinder missile and the Argentine aircraft operating at extreme range) they couldn't establish complete air superiority and prevent Argentine attacks during day or night nor stop the daily flights of C-130 Hercules transports to the islands.The Harrier GR.3, operated by the RAF, also saw combat during the Falklands War. They operated from Hermes and provided close support to the ground forces and attacked Argentine positions but were unable to destroy the Port Stanley runway.The Sea Harrier, modified to FRS2, saw combat during the Bosnia conflict, with one aircraft being shot down by Serbian defences in 1994. During the Kosovo War, combat patrols were flown, but no weapons were fired. The Sea Harrier patrolled over Iraq during the 12 years of enforcing no-fly zones. The AV-8B is an extensively redesigned aircraft with a new composite wing, new cockpit and avionics (e.g., FLIR and new bombing system), and more powerful engine. The new wing enables higher take-off weights and more ordnance. The payload was nearly double and the range much increased over the older design, one of the chief complaints with the older type. It was focused primarily on close-air support, and all the added capabilities came at the cost of about 50 mph (80 km/h) slower speed. The AV-8B was put into service in January 1985 at a cost of US$21.6 million each. The design was further developed into later types with high-speed, that placed less focus on payload and range.In the 2003 invasion of Iraq, Harrier II versions saw extensive usage by both the USMC and RAF. USMC Harriers were based on two USMC amphibious assault ships, USS Bataan (LHD-5) and USS Bonhomme Richard (LHD-6). Each carried 24 Harriers, about four times their normal complement of fixed-wing aircraft, and tried out the long dormant secondary purpose of the LHDs and LHAs, that of a small aircraft carrier, or sea control ship. RAF Harriers were shore-based in Kuwait. The current AV-8B Remanufacture Program converts older AV-8B day attack aircraft to the most recent production radar/night attack configuration. This radar-equipped version of the AV-8B, called the AV-8B II+, became operational in the summer of 1994. The AV-8B II+ uses the same AN/APG-65 radar system as the F/A-18 Hornet and is able to carry AIM-120 AMRAAM missiles, giving the aircraft a considerable increase in anti-aircraft capabilities. However, these missiles are most likely to be deployed as a means of self-defense or airbase defense instead of air superiority, because despite its agility, the Harrier is subsonic and therefore slower than most fighters.